1. Technical Field
The present invention relates to tunable optical devices, and more particularly to a reconfigurable multifunctional optical device including a spatial light modulator to selectively attenuate, condition and/or redirect at least one optical channel of a wavelength division multiplexing (WDM) optical signal.
2. Description of Related Art
MEMS micro-mirrors have been widely explored and used for optical switching and attenuation applications. The most commonly used application is for optical cross-connect switching. In most cases, individual micro-mirror elements are used to ‘steer’ a beam (i.e., an optical channel) to a switched port or to deflect the beam to provide attenuation on a channel-by-channel basis. Each system is designed for a particular ‘wavelength plan’—e.g. “X” number of channels at a spacing “Y”, and therefore each system is not ‘scalable’ to other wavelength plans.
Further, dynamic gain equalization (or “flattening”) is a critical technology for deployment of next-generation optical network systems. Dynamic gain equalizing filters (DGEF's) function by adding varying amounts of attenuation at different spectral locations in the signal spectrum of optical fiber communication systems. For instance, a DGEF may be designed to operate in the “C-band” (˜1530–1565 nanometers (nm)) of the communication spectrum that is capable of selectively attenuating spectrally concatenated “bands” of some preselected spectral width (e.g., 3 nm). The total number of bands within the DGEF is determined by the width of an individual band.
In the networking systems, it is often necessary to route different channels (i.e., wavelengths) between one fiber and another using a reconfigurable optical add/drop multiplexer (ROADM) and/or an optical cross-connect device.
One issue with the above optical MEMs device is that it is not “channel plan independent”. In other words, each MEMs device is limited to the channel spacing (or channel plan) originally provide. Another concern is that if the absolute value of a channel wavelength changes, a respective optical signal may begin to hit an edge of a corresponding mirror leading to large diffraction losses. Further, since each channel is aligned to an individual mirror, the device must be carefully adjusted during manufacturing and kept in alignment when operated through its full temperature range in the field.
It would be advantageous to provide an optical switching or attenuating device using a spatial light modulator and to combine multiple optical functions using a single spatial light modulator.